Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “host range determination”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1979

Host range conferred by the virulence-specifying plasmid of Agrobacterium tumefaciens.

The host range of Agrobacterium tumefaciens 1D1109, known to induce crown gall only on grapevine (Vitis spp.), was extended to include many plant species by transferring a tumor-inducing plasmid (pTi) from strain 1D1, a broad-host-range pathogen. The pTi plasmid was mobilized by the conjugative plasmid pRK2, which was inserted into 1D1 by mating with Escherichia coli J53(pRK2). The resulting transconjugants were screened for their ability to induce crown gall tumors on hosts other than grapevine by inoculation into sunflower. Transconjugants that were virulent on sunflower were then tested on 36 different host plants and compared with host-limited strain 1D1109 and the donor strain. Two transconjugants induced tumors on the same 28 plant species as those of the original plasmid donor 1D1(pRK2) (pTi). These results show that pRK2 promoted transfer of the pTi plasmid and suggest that the pTi plasmid rather than the A. tumefaciens chromosome determined the host range of the pathogen. Insertion of pRK2 alone did not extend the host range of strain 1D1109. Insertion of pS-a into A. tumefaciens 1D1 by mating with E. coli J53-1 (pS-a) resulted in the concomitant loss of pTi and virulence. There appears to be incompatibility between pTi and pS-a.

Conjugation, Genetic↗
PubMed2002

[Antigen analysis of envelope gene products of avian leukosis virus subgroup J].

Envelope glycoprotein of avian leukosis virus Subgroup J (ALV-J) determines the host range of virus infection and cross-neutralization patterns. The truncated envelope genes of avian lecukosis virus subgroup J (ALV-J) were amplified by PCR and cloned them into pGEX-5X-3 vector for expressing envGST-fusion protein. Western blot analysis results showed that the products of truncated env gene expressed in Escherichia coli could reacted with G2, JE9 and I45 monoclonal antibodies (Mabs) specific to envelope protein of ALV-J. Using different Mabs to map the epitopes in the expressed truncated gp85 GST fusion protein, the results showed that Mab G2 and JE9 antibodies recognizing epitope in gp85 was localized between amino acid 65-155. Mab I45 reacted with the epitope at the location of amino acid 156-233. It indicated that the specificity of subgroup J virus is determined by the gp85 peptide since GST-gp85 protein expressed in Escherichia coli is not glycosylated.

Antibodies, Monoclonal↗
PubMed2001

Genome replication and postencapsidation functions mapping to the nonstructural gene restrict the host range of a murine parvovirus in human cells.

The infection outcome of the Parvoviridae largely relies on poorly characterized intracellular factors modulated by proliferation, differentiation, and transformation of host cells. We have studied the interactions displayed by the highly homologous p and i strains of the murine parvovirus minute virus of mice (MVM), with a series of transformed cells of rat (C6) and human (U373, U87, SW1088, SK-N-SH) nervous system origin, seeking for molecular mechanisms governing parvovirus host range. The MVMp infection of C6 and U373 cells was cytotoxic and productive, whereas the other nervous cells behaved essentially as resistant to this virus. In contrast, MVMi did not complete its life cycle in any of the human nervous cells, though it efficiently killed the astrocytic tumor cells by two types of nonproductive infections: (i) normal synthesis of all viral macromolecules with a late defect in infectious virion maturation and release to the medium in U373; and (ii) high levels of accumulation of the full set of viral messenger RNAs and of both nonstructural (NS-1) and structural (VP-1 and VP-2) proteins, under a very low viral DNA amplification, in U87 and SW1088 cells. Further analyses showed that U87 was permissive for nuclear transport of MVMi proteins, leading to efficient assembly of empty viral capsids with a normal phosphorylation and VP1-to-VP2 ratio. The DNA amplification blockade in U87 occurred after conversion of the incoming MVMi genome to the monomeric replicative form, and it operated independently of the delivery pathway used by the viral particle, since it could not be overcome by transfection with cloned infectious viral DNA. Significantly, a chimeric MVMi virus harboring the coding region of the nonstructural (NS) gene replaced with that of MVMp showed a similar pattern of restriction in U87 cells as the parental MVMi virus, and it attained in U373 cultures an infectious titer above 100-fold higher under equal levels of DNA amplification and genome encapsidation. The results suggest that the activity of complexes formed by the NS polypeptides and recruited cellular factors restrict parvovirus DNA amplification in a cell type-dependent manner and that NS functions may in addition determine MVM host range acting at postencapsidation steps of viral maturation. These data are relevant for understanding the increased multiplication of autonomous parvovirus in some transformed cells and the transduction efficacy of nonreplicative parvoviral vectors, as well as a general remark on the mechanisms by which NS genes may regulate viral tropism and pathogenesis.

Animals↗
PubMed1983

Site-specific recombination by Gin of bacteriophage Mu: inversions and deletions.

A 3000-bp invertible segment in the DNA of bacteriophage Mu determines the host range of the phage. The inversion is catalyzed by the phage-coded protein Gin; the recombination sites are short inverted repeats. Gin protein is only made in low amounts by Mu. To further investigate the Gin-mediated recombination reaction a Gin overproducing strain was constructed. The gin gene was cloned on a plasmid behind the PL-promotor of phage lambda. This results in a 100-fold higher inversion frequency of a Mu gin phage as compared to the situation when Gin is expressed from its own promoter. A test system was developed suitable for the detection of Gin action in vivo and in vitro: the lacZ gene of E. coli was cloned within the invertible region in such a way that it is only expressed when the region is in one specific orientation. Thus inversions can be detected or selected as a switch from Lac- to Lac+. This system was used to determine the inversion frequency under different experimental conditions. The ability of Gin to catalyze deletions was investigated by inverting in vitro one of the two recombination sites using restriction enzymes and genetically marking the DNA between those sites. Deletions do occur, although at a lower frequency than inversions.

Bacterial Proteins↗
PubMed2000

Viral impacts on total abundance and clonal composition of the harmful bloom-forming phytoplankton Heterosigma akashiwo.

Recent observations that viruses are very abundant and biologically active components in marine ecosystems suggest that they probably influence various biogeochemical and ecological processes. In this study, the population dynamics of the harmful bloom-forming phytoplankton Heterosigma akashiwo (Raphidophyceae) and the infectious H. akashiwo viruses (HaV) were monitored in Hiroshima Bay, Japan, from May to July 1998. Concurrently, a number of H. akashiwo and HaV clones were isolated, and their virus susceptibilities and host ranges were determined through laboratory cross-reactivity tests. A sudden decrease in cell density of H. akashiwo was accompanied by a drastic increase in the abundance of HaV, suggesting that viruses contributed greatly to the disintegration of the H. akashiwo bloom as mortality agents. Despite the large quantity of infectious HaV, however, a significant proportion of H. akashiwo cells survived after the bloom disintegration. The viral susceptibility of H. akashiwo isolates demonstrated that the majority of these surviving cells were resistant to most of the HaV clones, whereas resistant cells were a minor component during the bloom period. Moreover, these resistant cells were displaced by susceptible cells, presumably due to viral infection. These results demonstrated that the properties of dominant cells within the H. akashiwo population change during the period when a bloom is terminated by viral infection, suggesting that viruses also play an important role in determining the clonal composition and maintaining the clonal diversity of H. akashiwo populations. Therefore, our data indicate that viral infection influences the total abundance and the clonal composition of one host algal species, suggesting that viruses are an important component in quantitatively and qualitatively controlling phytoplankton populations in natural marine environments.

DNA Viruses↗
PubMed1996

Mutations within the 5' nontranslated RNA of cell culture-adapted hepatitis A virus which enhance cap-independent translation in cultured African green monkey kidney cells.

Mutations in the 5' nontranslated RNA (5'NTR) of an attenuated, cell culture-adapted hepatitis A virus (HAV), HM175/P16, enhance growth in cultured African green monkey kidney (BS-C-1) cells but not in fetal rhesus monkey kidney (FRhK-4) cells (S. P. Day, P. Murphy, E. A. Brown, and S. M. Lemon, J. Virol. 66: 6533-6540, 1992). To determine whether these mutations enhance cap-independent translation directed by the HAV internal ribosomal entry site (IRES), we compared the translational activities of the 5'NTRs of wild-type and HM175/P16 viruses in two stably transformed cell lines (BT7-H and FRhK-T7) which constitutively express cytoplasmic bacteriophage T7 RNA polymerase and which are derived from BS-C-1 and FRhK-4 cells, respectively. Translational activity was assessed by monitoring expression of a reporter protein, chloramphenicol acetyltransferase (CAT), following transfection with plasmid DNAs containing bicistronic T7 transcriptional units of the form luciferase-5'NTR-CAT. In both cell types, transcripts containing the 5'NTR of HM175/P16 expressed CAT at levels that were 50- to 100-fold lower than transcripts containing the IRES elements of Sabin type 1 poliovirus or encephalomyocarditis virus, confirming the low activity of the HAV IRES. However, in BT7-H cells, transcripts containing the 5'NTR of wild-type virus. This translational enhancement was due to additive effects of a UU deletion at nucleotides 203 and 204 and a U-to-G substitution at nucleotide 687 of HM175/P16. These mutations did not enhance translation in FRhK-T7 or Huh-T7 cells (a T7 polymerase-expressing cell line derived from human hepatoblastoma cells) or in vitro in rabbit reticulocyte lysates. These results demonstrate that mutations in the 5'NTR of a cell culture-adapted HAV enhance viral replication by facilitating cap-independent translation in a cell-type-specific fashion and support the concept that picornaviral host range is determined in part by differences in cellular translation initiation factors.

Animals↗
PubMed2026

Genomic characterization and therapeutic potential of five broad-spectrum lytic bacteriophages against multidrug-resistant avian pathogenic Escherichia coli (APEC).

UNLABELLED: Colibacillosis, caused by avian pathogenic Escherichia coli (APEC), results in substantial economic losses in global poultry production. The emergence of multidrug-resistant (MDR) APEC poses zoonotic risks through horizontal transfer of antimicrobial resistance (AMR) genes. Bacteriophage therapy emerges as a safe alternative to antibiotherapy; however, comprehensive characterization of phages targeting MDR-APEC from diverse geographical regions remains limited. We isolated five lytic bacteriophages from poultry fecal samples collected from five Indian states and characterized them through morphological analysis, physiological stability testing, whole-genome sequencing, and in vivo efficacy assessment. Host range was determined against APEC isolates, and therapeutic potential was validated in the Galleria mellonella infection model. All phages showed Myovirus-like morphology and stability across physiologically relevant temperatures (up to 55°C-70°C) and pH conditions (3-11). Phages were classified as Escherichia phage vB_EcoM_fRPOT1, vB_EcoM_fDMYT1, vB_EcoM_fBSZT1, vB_EcoM_fUAMT1, and vB_EcoM_fPKPT2. Their genome size ranges from 170 to 356 kb, belonging to three distinct genera: Dhakavirus, Gaprivervirus, and Asteriusvirus. Genomic analysis confirmed the absence of antimicrobial resistance, virulence, toxin, or lysogeny genes. Fifty-one APEC strains were isolated, of which 23 (45.1%) were MDR. Individual phages lysed 37%-51% of tested APEC and 17%-39% of MDR strains. Three phages (fBSZT1, fUAMT1, and fPKPT2) significantly improved larval survival to 60%-80% at an MOI of 10 in G. mellonella infection models compared to the untreated control. This study establishes a well-characterized phage bank targeting MDR-APEC strains, providing a foundation for developing phage-based interventions to reduce antibiotic dependency and mitigate AMR transmission risks under the One Health framework. IMPORTANCE: The overuse of antibiotics in poultry farming has created a crisis. The multidrug-resistant (MDR) bacteria threaten both animal health and human safety through the food chain. When antibiotics fail, farmers face devastating losses, and resistant bacteria can transfer to humans through consumption or environmental contamination. Bacteriophages offer a practical solution as they kill target bacteria without harming beneficial microbes or leaving chemical residues. Our comprehensive characterization confirms that these five phages are safe and effective as they lack any resistance or toxin genes and rescue 60%-80% of infected larvae. This represents a characterized phage bank targeting the specific resistant strains in Indian poultry. By providing a validated alternative to antibiotics, this work supports sustainable food production while reducing the spread of antimicrobial resistance from farms to humans.

Animals↗
PubMed2002

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗
PubMed1986

Control of replication of the broad host range plasmid RSF1010: the incompatibility determinant consists of directly repeated DNA sequences.

A 500 bp DNA fragment located in the vicinity of the origin of replication of plasmid RSF1010 was cloned into the plasmid vector pBR322 and shown to exhibit incompatibility against parental RSF1010. The rightmost region of this fragment contains three perfect 20 bp direct repeats and a fourth half-repeat of 11 bp, as shown by DNA sequencing. Deletion of the four repeats from the cloned fragment resulted in complete loss of incompatibility whereas partial deletion of the repeated sequence resulted in a concurrent decrease in the expression of incompatibility. We conclude that the incompatibility determinant of RSF1010 is defined by the four repeats and also that the incompatibility expressed is not very strong, since the presence of about 1.5 times as many copies of the repeated sequence as are normally in a cell does not cause a total switch off of RSF1010 replication, but only a 40% reduction in the rate of replication.

DNA Replication↗
PubMed2005

Characterization of a potyvirus isolated from Tradescantia fluminensis in northern Italy.

We isolated a potyvirus from Tradescantia fluminensis that was causing leaf distortion and mild mosaic. We cloned and sequenced a 1500 bp cDNA obtained by RT-PCR corresponding to the 3' proximal region of the genome. We determined the host range and tested a series of potyviral antisera against our tradescantia virus isolate by immuno-enzymatic methods. Based on our results, we suggest that our viral isolate could be considered a new potyvirus species named Tradescantia mild mosaic potyvirus. Phylogenetic analysis confirmed that Tradescantia mild mosaic virus belongs to the genus Potyvirus within the family Potyviridae, but the virus could not be assigned to any of the potyvirus groupings recently defined.

Amino Acid Sequence↗
PubMed2006

Molecular epidemiology and phylogenetic analysis of a marine fish infectious spleen and kidney necrosis virus-like (ISKNV-like) virus.

Infectious spleen and kidney necrosis virus-like (ISKNV-like) virus causes a serious systemic disease with high morbidity and mortality of freshwater and marine fishes. Based on the ISKNV putative major capsid protein (MCP), the vascular endothelial growth factor (VEGF), the mRNA capping enzyme (Capping), and the tumor necrosis factor receptor-associated protein (TNFR) genes, primers were designed and used in PCR to determine the host range of ISKNV-like viruses. From the sampling of >1600 marine fishes representing 6 orders, 25 families, and 86 species collected in the South China Sea, 13 cultured fish species (141 fish) and 39 wild fish species (102 fish) were confirmed hosts of ISKNV-like viruses. The average percentage of infection of ISKNV-like viruses was 14.6%. The results from phylogenetic analysis of these genes revealed that ISKNV-like viruses could be placed into two clusters: cluster I was more related to ISKNV; cluster II included OSGIV (orange-spotted grouper iridovirus) and RBIV (rock bream iridovirus), and was quite different from ISKNV. The results of this study can contribute to the prediction and prevention of ISKNV disease outbreaks.

Animals↗
PubMed2006

Sequence analysis and receptor specificity of the hemagglutinin of a recent influenza H2N2 virus isolated from chicken in North America.

Influenza viruses bind host cells following an interaction between the viral hemagglutinin (HA) protein and host cell sialylated glycoproteins and glycolipids. Differences in binding affinities of the HAs for different types of sialic acid linkages (alpha2-3 vs. alpha2-6) contribute to determining the host range of an influenza virus. The ability of an avian influenza virus HA to bind the human form of the receptor may be one requirement for an avian virus to propagate in the human population. In this paper, we describe the characterization of the HA from an H2N2 virus isolated from a Pennsylvania chicken farm in 2004. Sequence analysis revealed that this HA is a member of the Eurasian clade, and receptor binding studies show that it maintains its specificity for the avian influenza virus alpha2-3 linked sialic acid receptor.

Amino Acid Sequence↗
PubMed2005

Complete genome sequence and biological characterizations of a novel goose paramyxovirus-SF02 isolated in China.

A paramyxovirus designated as APMV-1 (NDV) isolate SF02 (abbre. as SF02) was recently isolated from goose in China. SF02 was identified as a member of Newcastle disease virus (NDV) genotype VII. NDV strains are generally pathogenic only for fowls, including chicken and pigeon, and not for waterfowls such as goose and duck, whereas SF02 is highly pathogenic for both fowls and waterfowls. In the present study the complete genome consisting of 15, 192 nucleotides of SF02 was sequenced. Genomes of SF02 and all known APMV-1, Strains contain 6 ORFs in the order of NP-P-M-F-HN-L, and that of SF02 had an extra 6 nts between NP and P genes. Moreover, an anti-sense ORF consisting of 549 nt at the 1960 to 1412 and deduced 182 amino acids was found in SF02. The SF02 genome shared 83% identity and its 6 ORFs 81.9-86.1% identities with the reference APMV-1 strains. The possible mechanism determining different host range and pathogenicity is discussed based on genetic analyses.

Amino Acid Sequence↗
PubMed1984

Involvement of the invertible G segment in bacteriophage mu tail fiber biosynthesis.

The orientation [G(+) or G(-)] of the invertible G segment of bacteriophage Mu DNA determines the host range specificity of the phage particles. In this study the hypothesis that the G segment genes are involved in synthesis of Mu tail fibers has been tested. Serum blocking power (SBP) assays demonstrated that among Mu late gene mutants only those defective in genes S or U encoded by the G segment were defective in G(+) SBP and that they lacked the same antigens. Electron microscopy of lysates produced by inversion-defective gin mutants (isolated by their inability to complement a hin inversion-defective mutant of the Salmonella phase variation segment) showed that G(+) phages with amber mutations in S or U made tail-fiberless particles with contracted tail sheaths. Inversion of G to the G(-) orientation or suppression of the amber mutations restored the normal phage particle morphology. These experiments demonstrate that genes S and U are required for Mu G(+) tail fiber biosynthesis and/or attachment.

Antigens, Viral↗
PubMed1985

Crossover sites cix for inversion of the invertible DNA segment C on the bacteriophage P7 genome.

The bacteriophage P7 genome contains an invertible DNA segment called C which determines its host range. P7 C(+) phages produce plaques on Escherichia coli K12. The C segment consists of a 3-kb unique sequence and 0.62-kb inverted repeats of which one carries an internal 0.2-kb deletion. This deletion has been mapped within the right inverted repeat in the C(+) orientation. The crossover sites cix for inversion of the C segment do not map at the inside boundaries of the inverted repeats, as had been proposed. They are localized at the external ends of these repeats. Thus organization of the C segment in phage P7 is analogous to that in the related phage P1.

Base Sequence↗
PubMed1989

A novel exopolysaccharide can function in place of the calcofluor-binding exopolysaccharide in nodulation of alfalfa by Rhizobium meliloti.

We have found that R. meliloti strain Rm1021, which is known to synthesize a Calcofluor-binding exopolysaccharide (EPS I), also has a cryptic capacity to synthesize a second exopolysaccharide (EPS II). Structural analysis of EPS II has shown that it differs in many respects from EPS I. Genetic analysis indicates that EPS II synthesis requires the products of at least seven loci on the second symbiotic megaplasmid of R. meliloti, and is induced by a mutation, expR101, which causes increased transcription of these genes. Synthesis of EPS II suppresses the symbiotic defects of EPS I-deficient strains on Medicago sativa (alfalfa), but not on four other plants that are normally hosts for Rm1021. These observations suggest that structural features of bacterial exopolysaccharides are involved in the determination of host range. The implications of these results for models of exopolysaccharide function, such as serving as signals to the plant or shielding the bacteria from plant defense responses, are discussed.

Benzenesulfonates↗